A punch die used for punch press is provided with a stripper plate for pressing down the die to a plate-shaped workpiece, while the workpiece is processed in a punching process with a punch, for the purpose of preventing a deformation of punching during the punching process. When the edge part of the punch is worn, the punch is removed from the punch die, and the edge part is ground again. In this case, it is necessary to remove the stripper plate from the punch die. With this background, proposals have been made on a configuration which allows the stripper plate to be mounted on and detached from the punch die easily. Such a configuration is disclosed, for example, in a Patent Brochure of Japanese National Publication of Translation Version (Kohyo) No. 2005-528986 (Patent Document 1).
A punch die described in Patent Document 1 has a configuration as shown in FIG. 1. Specifically, the punch die 1 includes a cylindrical punch guide 5 for guiding a punch body 3 movable upward and downward. A retainer collar 7 is attached to an end side of this punch guide 5 with a bolt or the like. In addition, a punch head 11 is attached to an end portion of a cylindrical punch driver 9 adjustably screwed to an adjustable screw part provided to an end side of the punch body 3. A stripper spring 13 is set resiliently between the punch head 11 and the retainer collar 7.
A punch block 17 is attached in a detachable and replaceable manner to the other end side of the punch body 3 with a bolt 15. A punch edge part 19 is formed in a front end portion of this punch block 17. A disk-shaped stripper plate 21 surrounding this punch edge part 19 is mounted in a detachable and replaceable manner on a front end portion of the punch guide 5.
Specifically, a cylindrical holder 23 for holding the stripper plate 21 to the front end portion of the punch guide 5 is fitted into an inner circumferential surface of the front end portion thereof to be movable upward and downward. Furthermore, springs 25 each for always biasing the holder 23 upward are set resiliently in spring housing concave parts provided in multiple locations on the outer circumferential surface of the holder 23, respectively. Moreover, plate lock-holding pieces 27 are respectively provided in other multiple locations on the outer circumferential surface of the holder 23 to be swingable (inward and outward) in radial directions. The plate lock-holding pieces 27 are each for integrally locking and fixing the stripper plate 21 to the holder 23 by engaging with an annular groove 21G formed in the outer circumferential surface of the stripper plate 21.
In addition, lock buttons 31 are respectively provided, movably in radial directions (radius directions), in yet other multiple locations of the outer circumferential surface of the holder 23. The lock buttons 31 are engageable with, and detachable from, lock holes 29 which extend in the radial directions (radius directions), and which are respectively provided to multiple locations in the punch guide 5. Incidentally, the lock buttons 31 are always biased outward by their respective built-in springs 33.
In the foregoing configuration, as shown in the drawing, in a state in which: the holder 23 is inserted in the punch guide 5 against biasing forces from the respective springs 25; the plate lock-holding pieces 27 provided to the holder 23 are slid inward by the inner circumferential surface of the front end of the punch guide 5, and thus holds the stripper plate 21; and the lock buttons 31 provided to the holder 23 engage with the respective lock holes 29 of the punch guide 5, the stripper plate 21 is in the state of being integrated with the punch guide 5, and is thus not detachable.
The stripper plate 21 is detached from the punch guide 5 and replaced with a new one in a following way. Specifically, the lock buttons 31 provided in the multiple locations are simultaneously pressed against the respective springs 33, and thereby the engagement of the lock holes 29 with the respective lock buttons 31 is released. With this operation, the holder 23 is moved upward in FIG. 1 by the biasing forces from the respective springs 25. Once the holder 23 is moved upward, the plate lock-holding pieces 27 become slidable outward, and thus the fixation of the stripper plate 21 is released. For this reason, it is possible to remove the stripper plate 21 from the holder 23.
Conversely, by setting the stripper plate 21 on the holder 23, and subsequently by pressing the holder 23 toward the inside of the punch guide 5 against the biasing forces from the respective springs 25, the stripper plate 21 is fixed. Specifically, once the holder 23 is pressed and moved toward an inner side of the punch guide 5, the plate lock-holding pieces 27 move inward in their respective radial directions (radius directions), and thus integrally fix the stripper plate 21. Thereafter, once the holder 23 is pressed, the lock buttons 31 provided to the holder 23 engage with the respective lock holes 29 provided to the punch guide 5, and thus the holder 23 is fixed thereto. Thereby, the stripper plate 21 is integrated with the punch guide 5.
As learned from the foregoing descriptions, the conventional configuration has a problem that the multiple lock buttons 31 have to be simultaneously pressed against the respective springs 33. In addition, because the holder 23 is pushed upward by the biasing forces from the springs 25, the holder 23 may sometimes be pushed up so forcefully and abruptly, if the punch edge part 19 in the punch block 17 is relatively large and the stripper plate 21 is relatively light in weight, that there is another problem that an operator feels that the stripper plate is unstable. Moreover, in the case of the conventional configuration, after the stripper plate 21 is repeatedly mounted and detached, some plate lock-holding pieces 27 may break. For these reasons, further improvements are requested.
The present invention has been made for the purpose of solving the above-described problems. An object of the present invention is to provide a stripper plate mounting apparatus which allows an adaptor holding a stripper plate to be fixed to, and detached from, a punch guide easily.